1. Technical Field
The present disclosure relates to an electronic apparatus and method. More particularly, the present disclosure relates to a capacitive sensor and a capacitive sensing method with a calibration mechanism.
2. Description of Related Art
Various factors can change the structure of a capacitor, and the resulting change in capacitance can be used to sense those factors. Therefore, capacitors can be used as the sensor in condenser microphones, where one plate is moved by air pressure, relative to the fixed position of the other plate. Some accelerometers or gyroscopes use MEMS capacitors etched on a chip to measure the magnitude and direction of the acceleration vector as well. The MEMS capacitors are used to detect changes in acceleration, e.g. as tilt sensors or to detect free fall. Consequently, the changes in the acceleration, the angular acceleration and the volume can be detected by the variation of the charge stored in the capacitors that are designed carefully.
However, some non-ideal effects exist even if the capacitors are designed carefully. For instance, an ideal capacitor generates no capacitance variation when no stimulus is applied to the capacitor. However, if the capacitor is not symmetrical, an initial offset may produce an undesired capacitance variation even no stimulus is applied to the capacitor. On the other hand, two similar capacitors receiving the same stimulus may generate different amount of capacitance variation due to the slightly different sensitivity determined by the process variables of the two similar capacitors. However, in applications demanding a high level of precision, the non-ideal effects described above may result in a sensing result with a large amount of error.
Accordingly, what is needed is a capacitive sensor and a capacitive sensing method with a calibration mechanism. The present disclosure addresses such a need.